//The MIT License
//
//Copyright (c) 2009 nodchip
//
//Permission is hereby granted, free of charge, to any person obtaining a copy
//of this software and associated documentation files (the "Software"), to deal
//in the Software without restriction, including without limitation the rights
//to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//copies of the Software, and to permit persons to whom the Software is
//furnished to do so, subject to the following conditions:
//
//The above copyright notice and this permission notice shall be included in
//all copies or substantial portions of the Software.
//
//THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//THE SOFTWARE.
package tv.dyndns.kishibe.server;

import java.util.Random;

public class Utility {
	private static Utility INSTANCE = new Utility();

	public static Utility getInstance() {
		return INSTANCE;
	}

	private final Random random = new Random();

	private static final int FILE_TITLE_LENGTH = 8;

	public Utility() {
	}

	public int[] makePermutationArray(int n) {
		if (n <= 0) {
			return new int[0];
		}
		int perm[] = new int[n];
		for (int i = 0; i < n; ++i) {
			perm[i] = i;
		}

		for (int i = 0; i < n; ++i) {
			int index = random.nextInt(n);
			int temp = perm[i];
			perm[i] = perm[index];
			perm[index] = temp;
		}

		return perm;
	}

	public String createFileName() {
		final StringBuffer stringBuffer = new StringBuffer();
		for (int i = 0; i < FILE_TITLE_LENGTH; ++i) {
			final char c = (char) (Math.abs(random.nextInt(26)) + 'a');
			stringBuffer.append(c);
		}
		return stringBuffer.toString();
	}
}
